By way of example, a medical instrument is known from the patent document U.S. Pat. No. 5,570,770. Medical instruments for medical diagnosis or therapy may have an x-ray emitter and an x-ray detector, each being within a housing. The x-ray emitter and the x-ray detector are arranged at a distance from one another, with a patient to be examined or to be treated being placed between the x-ray emitter and the x-ray detector. The x-ray emitter and the x-ray detector are positioned relative to the body of the patient such that an image of a desired cross-section of the body interior may be recorded. The alignment and positioning of the medical instrument may be undertaken with the aid of a motor-driven drive.
Such instruments may be equipped with a C-arm (e.g., with an arcuate holder that may be rotated about several planes with the aid of a guide-rail system). During the use of the medical instrument, a moved part (e.g., the x-ray detector) may come close to the object to be examined in order to achieve the desired image quality. The x-ray detector has a comparatively large frontal area for receiving the x-ray beams, and every point on this frontal area or on a circumference may come into contact with the patient to be examined. Such a collision may occur in any movement direction of the x-ray detector. This is undesirable, and therefore, an instrument of this type is equipped with a detection device for identifying the collision with an object.
If contact between the movable part of the instrument and the object is identified, the movement of the aforementioned instrument may be stopped in order thereby to minimize the severity of the aftermath of a collision. In the aforementioned patent document U.S. Pat. No. 5,570,770, a medical x-ray instrument that is equipped with an electrical detection device for identifying collisions is described. Sensor devices in the instrument are configured to measure the current or power taken up by the drive motor. These variables provide an indication of the current force exerted on the movable part. This current value may be compared to an expected value for the aforementioned force. If the difference between the current value and the expected value exceeds a predetermined threshold, the assumption is made that the movement of the movable part is impeded by an object and hence that a collision is taking place. Accordingly, an alarm signal is generated, and the movement is stopped.
Housing claddings of movable medical instruments or parts of claddings, in which a collision with an object has an effect on an electrical switch or on electrically switchable contacts, are also known. By way of example, such housing claddings are mounted resiliently, with the positional displacement thereof by a collision being identified. The switching signals obtained therefrom are used to switch off a movement of the medical instrument.